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Exercise Physiology > Factors Affecting Performance > Flashcards

Factors Affecting Performance Flashcards

1
Q

Factors Affecting Performance

A
  1. Diet
  2. CNS Function
  3. Strength/Skills
  4. Environment
  5. Energy Production - anaerobic sources
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2
Q

Diet

A
  1. Carbohydrate

2. Water Intake

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3
Q

Energy Production - anaerobic sources

A
  1. [PC]
  2. Glycolysis

Anaerobic Sources

  1. VO2 max
  2. Cardiac Output
  3. O2 delivery
  4. [Hb]
  5. PO2
  6. O2 extraction
  7. Mitochondria
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4
Q

Environment

A
  1. Altitude
  2. Heat
  3. Humidity
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5
Q

Strength’Skill

A
  1. Practice
  2. Natural Endowment
  3. Body type
  4. Muscle Fiber Type
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6
Q

CNS Function

A
  1. Arousal

2. Motivation

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7
Q

Sites of Fatigue

A

Central and peripheral

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8
Q

Fatigue

A

Inability to maintain power output or force during repeated muscle contraction

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9
Q

Central Fatigue

A

CNS

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10
Q

Peripheral Fatigue

A
  1. Neural Factors
  2. Mechanical Factors
  3. Energetic Contraction
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11
Q

Peripheral Fatigue is

A

the big picture but central fatigue will cost you the race

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12
Q

Possible sites of fatigue

A
  1. Psyche brain (motor unit recruitment/motivation)
  2. Spinal Cord (reflex drive)
  3. Peripheral Nerve (Neruomuscular transmission)
  4. Muscle sarcolemma (Muscle action potential)
  5. Transverse tubular system (K, Na, excitation)
  6. Calcium release (activation, energy supply)
  7. Actin-myosin interaction
  8. Cross bridge tension and heat
  9. Force Power output
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13
Q

Central Fatigue listed as a site of fatigue due to

A
  1. Reduction in motor units activated
  2. Reduction in motor unit firing frequency
  3. CNS arousal can alter the state of fatigue
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14
Q

CNS arousal can alter the state of fatigue

A

By facilitating motor unit recruitment to increase strength

  1. increasing motivation (shouting during the exertion)
  2. Physical or mental diversion (i.e. contracting non-fatiguing muscles during the rest period or doing arithmetic b/w fatiguing bouts.)
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15
Q

Excessive endurance training - overtraining

A
  1. Reduced performance, prolonged fatigue, sleep disturbances, loss of appetite,
  2. Evidence that increases r decreases in brain serotonin during prolonged exercise either hastens or delays fatigue respectively
  3. New evidence points to ration of serotonin linked to fatigue, sleepiness, depressed mood) to dopamine that either leads to fatigue or arousal
  4. Brain levels of NE also contribute to fatigue or arousal
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16
Q

Central governor model has some criticism

A
  1. Focuses on conscious and subconscious brain not spinal cord or motor unit
  2. Proposes that the brain regulates exercises intensity in an effort to protect the body from exercise-related damage or by disrupting cellular homeostasis
  3. The central governor limits/control exercise intensity vy neurally recruiting a certain amount of motor units innervating skeletal muscle
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17
Q

Peripheral Fatigue: Neural Factors

A
  1. Majority of evidence for fatigue points to peripheral factors where neural mechanical or energetic events can reduce tension development
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18
Q

Neural Factors

A

Sarcolemma and transverse tubules - relates to ability of muscle membrane to conduct an action potential

  1. Inability of Na/K pump to maintain action potential amplitude
  2. Na/K pump capacity can be improved by training
  3. Gradual depolarization of sarcolemma can result in action potential block in the T-tubules which signals calcium release from SR
  4. Reduction in calcium release from SR affects muscle contraction
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19
Q

Neuromuscular Junction

A

Not a site of fatigue

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20
Q

Peripheral Fatigue Mechanical Factors

A
  1. Cross Bridge Cycling and tension development
  2. High H+ Concentration may contribute to fatigue
  3. Longer relaxation time is a sign of fatigue
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21
Q

Cross bridge cyclin and tension development depend on

A
  1. Arrangement of actin and myosin
  2. Calcium being available to bind with troponin
  3. ATP availability needed for activation (causes movement) and dissociation (causes relaxation) of cross bridges
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22
Q

High H+ concentrations may contribute to fatigue by

A
  1. Reducing the force per cross-bridge
  2. Reducing the force generated at given Calcium concentration
  3. Inhibiting calcium release from SR
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23
Q

Longer Relaxation time is a sign of fatigue

A
  1. Relates to time of peak tension development to baseline tension
  2. Due to slower cross-bridge cycling
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24
Q

Peripheral Fatigue: Energetics of Contraction

A
  1. Imbalance between ATP requirements and ATP generating capacity
  2. Rate of ATP utilization is slowed faster than rate of ATP generation due to cellular fatigue mechanism
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25
Q

Imbalance between ATP requirements and ATP generating capacity

A

Accumulation of inorganic phosphate occurs when ATP generating mechanisms cannot keep up with ATP usage which

  1. inhibits maximal force
  2. Reduces cross-bridge binding to actin
  3. inhibits Ca release from SR
26
Q

Rate of ATP utilization is slowed faster than rate of ATP generation due to cellular fatigue mechanism

A

This is done as a protective mechanism in order to maintain ATP concentration and homeostasis. In other words, ATP availability to the cell never really run out. Factors that cause fatigue cause a reduction in rate of ATP utilization

27
Q

Radical Production During Exercise Contributes to Muscle Fatigue

A
  1. Key contributor to muscle fatigue during high intensity or prolonged exercise greater than or equal to 30 minutes
28
Q

Exercise promotes free radical formation

A

Molecules that contain unpaired electrons in outer orbital and are capable of damaging proteins lipids and DNA

29
Q

Free Radicals Can Contribute to Fatigue by

A
  1. Damage to contractile proteins (myosin and troponin) reduces calcium sensitivity of these myofilaments which limits the number of cross bridges in the strong binding state and depress Na/K pump activity in muscle due largely to disruption of K homeostasis
30
Q

Optimal levels of antioxidants can postpone fatigue

A

high doses of antioxidants can impair muscle function

31
Q

Muscle fiber recruitment in increasing intensities of exercises

A

Type 1 —) Type 2a —) Type 2x

32
Q

Up to 40% VO2 max type 1 fibers are recruited

A

reductions in O2 supply to this fiber would reduce tension development

33
Q

Type 2a fibers recruited at 40-75% VO2 max

A

If O2 delivery reduced or ability of fiber to use O2 reduced (reduced mitochondria) then tension development reduced

34
Q

Exercise > 75% VO2 max requires 2x fibers

A

Results in increased lactate and H+ production

35
Q

Events lasting less than 10 seconds

A

Shot put
High Jump
Long Jump
50-100 meter sprint

36
Q

Ultra short term performances are

A

dependent on recruitment of type 2 muscle fibers that generate great forces in a short period of time

37
Q

Max performances of ultra short term performances are limited by

A
  1. Fiber type distribution and number of fibers recruited which is influenced by motivation and arousal
  2. Optimal performance affected by skill and technique which are dependent on practice
38
Q

Ultra Short-Term Performances

A

Primary Energy Source is anaerobic - ATP-PC system and glycolysis - thus creatine supplementation may improve performance

39
Q

Factors affecting fatigue in ultra short term performance

A
  1. Practice
  2. Skill and technique
  3. Muscular Power
  4. Fiber type distribution and recruitment
  5. PC and glycolysis
  6. Motivation and arousal
40
Q

Short Term Performance

A

Events lasting 10-180 seconds

  1. 200-400 meter sprint
  2. 50-100 meter swim
41
Q

Shift from anaerobic to aerobic metabolism in short term performances

A
  1. 70% energy supplied anaerobically at 10s

2. 60% supplied aerobically at 180s

42
Q

Anaerobic glycolysis is

A

Primary energy source that results in elevated lactate and H+ levels and interferes with Ca binding with troponin for short term performances

43
Q

Ingestion of buffers may

A

Improve performance in short term performances

44
Q

Factors affecting Fatigue in the Short term

A
  1. Fiber type distribution and recruitment
  2. increasing muscle and blood H+ - buffer
  3. VO2
  4. Glycolysis and PC
45
Q

Moderate Length Performances

A

Events lasting 3-20 minutes (5 K run)

  1. 60% ATP generated aerobically at 3 min
  2. 90% ATP supplied aerobically at 20 min
46
Q

Performance limites in moderate length performances

A

the CVS and mitochondrial content

47
Q

High VO2 max is

A

Important in moderate length performances

  1. High maximal SV key to high CO
  2. High arterial O2 content is influenced by HGB content and inspired O2
48
Q

Moderate Length Performances

A

Require energy expenditure near VO2 max - type 2x fibers recruited - high level of lactate and H+ accumulation

49
Q

Is maximal oxygen uptake important in distance running performance

A

VO2 max sets the upper limit for ATP production in endurance events - even though race is not run at 100% VO2 max

Performance is also determined by %VO2 max at which runner can perform - estimated by lactate threshold or GET and running economy (moving at a faster rate of speed for the same amount of O2 consumption compared to someone who is slower at the identical O2 consumption

50
Q

Intermediate Length Performances

A
  1. Events lasting 21-60 minutes
  2. Predominantly aerobic - usually conducted at ,90% VO2 max
  3. High VO2 max is important
  4. High lactate threshold or GET
51
Q

Intermediate Length Performances

A

Other Important Factors
1. Running economy - due to both biochemical and bioenergetic factors and High percentage of type 1 muscle fibers

  1. Environmental Factors - due to heat, humidity (related to portion of cardiac output that will be directed to skin for cooling, this will affect HR at any given workload) and state of hydration this will affect HR at any given workload due to changes in plasma volume.
52
Q

Factors affecting Fatigue in aerobic performances lasting 21-60 minutes

A
  1. heat load
  2. steady state VO2
  3. Dehydration
  4. Lactate threshold
  5. % type 1 fibers
  6. biomechanics
  7. running economy
  8. bioenergetics
  9. running economy
53
Q

Long term performances

A

Events lasting 1-4 hours

54
Q

Environmental factors are

A

more important the longer the performance

55
Q

Maintaining a rate of carbohydrate utilization is an issue at durations greater than

A

1 hour because muscle and liver glycogen stores decline

  1. maintain carbohydrate oxidation by the muscle at >60% VO2 max
    1a. Fats can provide fuel below 60% VO2 max typically but carb oxidation allows for higher intensities to be maintained or performance will suffer
  2. Protection of membrane excitability (increased glucose supplementation during prolonged exercise suggests improvements in Na/K pump to maintain action potential amplitude and frequency during repeated stimulation
56
Q

Factors affecting fatigue in aerobic performances lasting 1-4 hours

A
  1. heat load
  2. dehydration
  3. Liver and muscle glycogen stores - supplement during exercise
  4. Diet
  5. Lactate threshold
  6. VO2 max
  7. % Type 1 fibers
  8. Biomechanics
  9. Bioenergetics
  10. Running economy

Diet, glucose supplementation and fluid ingestion during duration events are very important in order to prevent glycogen depletion

57
Q

Factors affecting performance in ultra endurance events

A

Examples:
166 km mountain run
Triple Iron Triathlon
24 hour rin

58
Q

Most important variables in ultra endurance events

A
  1. VO2 mac

2. % VO2 max that can be sustained

59
Q

Metabolic Responses during ultra endurance events

A
  1. Plasma FFA and fat oxidation is 3.5x higher after event consistent with exercise at
60
Q

Potential for hyponatremia during ultra endurance events is

A

high because sodium stores are diluted because of too much water ingestion only happens to 4% of athletes.

Exercise Physiology (3 decks)

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